Johnson, Debra, author
Routledge, Taylor & Francis group, 2003
Buku Teks
edited by Huub Ruel
Emerald, 2018
eBooks
Stopford, John Morton
Basic Books, 1972
Buku Teks
Rugman, Alan M., author
McGraw-Hill, 1985
Buku Teks
Dunning, John H
Addison-Wesley , 1992
Buku Teks